Conveying systems often serve the function of aligning and spacing articles on the conveying system to be processed by a downstream sorting system. Conventional conveyance systems typically involves controlling the articles in such a way that the articles leaving the induction subsystem have gaps between them that are close to a desired length. The desired gap may be variable depending upon the length and/or width of one or more of the pair of articles that define the gap, or the desired gap may be constant. Regardless of the criteria used to determine the length of the desired gap, the gap serves the purpose of facilitating the sorting of the articles. Sorting systems often function more effectively if the articles being sorted have a certain minimum gap between them. However, gaps exceeding this minimum will generally decrease the throughput of the conveying system. It is desirable to create gaps that balance sortation criteria while maximizing the throughput to the sorting and singulator apparatus; however, at the point of induction where the parcels are fed onto a plurality of conveyors from various feed points such as truck unloading stations, maximum efficiency is achieved by moving as many parcels as possible on a given area of the conveyor.
Due to the variability of the amount of product coming in on various infeed belts, imbalances occur at different merge areas in the conveying system causing large open spots on the collector belt, singulator belt and sorting area. This fact causes inefficiency, an unnecessary investment in equipment, and a degradation of overall throughput to the sorter. Conventional flow management systems count packages and/or control the speed of conveyors to orient or singulate packages and create a desired minimum gap there between for processing. Examples of these devices is set forth in the following patent and/or publication:
U.S. Pat. No. 5,165,520 teaches a conveying system which spaces parcels on a belt and includes a camera system which recognizes overlapping or crowding of parcels and diverts the offending parcels. U.S. Pat. No. 8,061,506 teaches merging articles onto conveyors using information gathered from optical sensors or cameras to recognize or create an gas on a collector belt and fill these gaps with a package from an infeed belt; however, Schafer does not discuss the method of processing information from cameras or optical sensors to control the concentration of same. Publication (WO200066280) describes a system using a camera to determine the number of parcels and uses this information to control the speed conveyors such as a parcel feeder conveyor, acceleration conveyor, buffer conveyor, singulator and transportation conveyor; however, the reference does not teach nor suggest the idea of controlling the speed of conveyance in order to maximize the area covered on the conveyor as a function of occupancy on a collector or just prior to singulator. U.S. Pat. No. 6,471,044 teaches that images are transferred to a control system where the images are interpreted to determine the number of packages and the average size of the packages to regulate the speed of the parcel feeder conveyor, buffer conveyor, acceleration conveyor, singulator, and transport conveyor, but not the density of the packages on a given area of the conveyor. U.S. Pat. No. 5,141,097 teaches analysis of an image supplied by a camera to provide an indication of the number of packages present in this image and increase the conveyor speed to obtain the desired throughput. U.S. Pat. No. 6,401,936 teaches a detection system for monitoring the stream of articles and identifying and/or tracking individual items passing through the system used in conjunction with a singulator, hold-and-release or strip conveyor downstream from the coarse singulator wherein the control system is utilized in connection with the detection system to regulate the flow of articles through the system by increasing the speed of the conveyor.
Flow management is an essential component of systems that incorporate linear parcel singulator. Flow conditions are typically controlled by one or more separation or accumulator devices in order to control the input flow to the system. The singulator serves as a buffering element in the system, but has its capacitive limits, and a degree of flow management is necessary to avoid over-feeding. A singulator will only allow a single file stream of parcels to exit. When excessive flow is input, parcels are re-circulated. If excessive input flow continues, an excessive number of items can accumulate within the singulator, eventually leading to jams and excessive parcel pressure and damage.
Conventional systems utilize methods of either counting carton feet or parcels released from the container unload conveyors, and adjusting the speeds of the unload conveyors to maintain the input flow at a manageable level for the singulator and sorter. The goal is to keep the system fed, without over-feeding. However, these current methods are fairly inaccurate and in order to avoid over-feeding, the calculations used in the algorithm must be fairly conservative in order to avoid over-feeding. Current FDXG systems have sorter capacity of 12,150 parcels per hour (pph) with a 12 inch gap at 540 feet per minute (fpm), and with a 20 inch average. The result is that the system throughput efficiency is limited, and typical sustained performance capability is only expected to be about 60% of sorter capacity. There is a need for a control system to maximize the occupancy and density of packages on a given area of a conveyor upstream of a singulator device or receiver.